a. Field of the Invention
This invention relates generally to apparatus for belling the ends of plastic pipe, and, in particular, to apparatus for providing a greatly accelerated rate for receiving cut plastic pipe and belling the same.
B. DESCRIPTION OF THE PRIOR ART
Within the last two decades, plastic piping has been accepted for a multitude of uses. It is ordinarily produced by a process of continuous extrusion and cut into desired lengths. The preferred manner of joining these lengths is by providing one end of each pipe with a "bell" of expanded inside diameter such that it permits a close fit within such belled end of the unbelled end of another pipe to be joined end-to-end thereto.
The belling process, as illustrated by the following patents and patent applications, viz. U.S. Pat. Nos. 3,360,826; 3,553,780 and 3,205,535. British Pat. No. 1,087,168 and U.S. patent applications Ser. Nos. 62,100 and 41,267 essentially involves conveying the pipe to be belled to a location where its end is disposed in proximity to a heater for softening, and a mandrel is inserted in the softened end to expand it into contact with some type of surrounding mold or clamping device to shape the outside of the pipe end. The thus-expanded pipe end must then be cooled so that the plastic sets in this outwardly forced new configuration. After cooling, both the mold or clamp and the mandrel are removed.
In all such belling apparatus heretofore devised, the belling process has been found to delay production of belled plastic pipe. Thus, extrusion and pulling the pipe from the extruder may occur at a rate as high as 2 feet per second. Cutting of the pipe with a saw may be almost instantaneous. Conveyors may be constructed to carry pipe as rapidly as each cut length of pipe is deposited in a conveyor. The belling process, however, has not been anywhere near as rapid. This is because it takes time both to heat up the pipe end for insertion of the mandrel or plug, and then to cool it down after the mandrel has been so inserted in the heatsoftened pipe end. At a very minimum, a period in excess of 30 seconds has been required to accomplish the belling of the end of a pipe.
Because of this time requirement of the belling process, either a belled-pipe manufacturing production line cannot be operated at the full speed of the extruder, puller, cutter and conveyor; or provision must be made to have the cut pipe lengths delivered sequentially to a battery of separate belling machines. The first alternative is costly from a production time standpoint, or may require that pipe production prior to belling be entirely separated from the belling operation, thereby introducing expensive handling and storage factors. The other alternative introduces some complex pipe-handling and transfer problems and also requires the pipe producer to purchase, set up and maintain the battery of separate belling machines.
Thus, prior to the present invention, the state of the art has been such that the belling of plastic pipe has constituted a severe limitation upon what would otherwise comprise a rapid pipe production line, with resultant increase in the cost of producing lengths of belled plastic pipe.